The detailed electron-microscopic and histochemical studies are being performed on cultured human muscle from patients with various neuromuscular disorders. The study will aid in the delineation of those features of diseases which are primarily myopathic from those which are due to influences external to the muscle fiber, such as microvascular changes, immunologic mechanisms and neuronal and axonal dysfunction. In disorders found to be primary myopathies, on the basis of the defect being perpetuated in culture, the steps of in vitro pathogenesis will be analyzed and maneuvers to convert to normality (in vitro "treatment" tried). Muscle fiber defects not being reproduced in vitro (resulting in normal growth) will, as a first approximation, be presumed to be secondary; consequently, we would attempt to produce the defect in vitro by manipulations of chemical, immunologic or other environmental factor of the cultures. BIBLIOGRAPHIC REFERENCES: V. Askanas, W. K. Engel, S. DiMauro, B. R. Brooks and M. Mehler: "Adult-onset Acid Maltase Deficiency. 0orphologic and Biochemical Abnormalities Reproduced in Cultured Muscle." N. Engl. J. Med. 294: 573-578, 1976. V. Askanas, S. DiMauro, M. Mehler, W. K. Engel: "Acid Maltase Deficiency: Reincarnation in Cultured Muscle Fibers of the Typical Morphological and Biochemical Defects." Arch. Neurol. 33: 391, 1976.